1. Field
This disclosure relates generally to capacitive touch pads, and more specifically, to a capacitive touch pad with adjacent touch pad electric field suppression.
2. Related Art
Touch sensors have been available for a number of years as a relatively inexpensive alternative to mechanical switches. One type of touch sensor, commonly known as a capacitive touch sensor, or pad, detects a change in capacitance when an object, such as a human finger, interacts with an electric field. In an application such as a telephone touch pad, a number of capacitive touch pads are arranged as an array, or matrix of touch pads spaced apart and arranged as the telephone design allows.
When designing capacitive touch pads, it can be difficult to isolate touch pad activations between adjacent pads. A capacitive coupling between adjacent pads may result in unintentional touch pad activations of adjacent pads. This problem is even more acute in small handheld devices having a relatively small total surface area for the touch pads. One way to suppress the capacitive coupling is to use a ground ring around each pad. However, the use of ground rings requires additional surface area that may not be available on small pads. Another way to isolate and prevent adjacent pad detection is in the detection algorithm software used by the detection hardware to detect pad touches. A problem with the detection algorithm is that sometimes the adjacent pad capacitance can be nearly the same as the capacitance of the touched pad.
Therefore, what is needed is a capacitive touch pad that solves the above problems.